四、MyBatis 框架 Dao 动态代理

1.1 步骤

（1）去掉之前编写的Dao 接口实现类

（2） getMapper 获取代理对象

只需调用 SqlSession 的 getMapper()方法，即可获取指定接口的实现类对象。该方法的参数为指定 Dao接口类的 class 值。

不使用工具类：

SqlSession session = factory.openSession();
StudentDao dao = session.getMapper(StudentDao.class);

使用工具类:

SqlSession sqlSession = MybatisUtils.getSqlSession();
// 这句代码可以自动创建dao接口的实现类对象
StudentDao dao = sqlSession.getMapper(StudentDao.class);

（3）使用 Dao 代理对象方法执行 sql 语句

@Testpublic void testSelectStudents() {/*** 使用mybatis的动态代理机制，使用SqlSession.getMapper(dao接口)* getMapper能够获取dao接口对应的实现类对象。*/SqlSession sqlSession = MybatisUtils.getSqlSession();StudentDao dao = sqlSession.getMapper(StudentDao.class); // 这句代码可以自动创建dao接口的实现类对象//调用dao的方法，执行数据库的操作List<Student> students = dao.selectStudents();for (Student student : students) {System.out.println("学生=" + student);}}@Testpublic void testInsertStudents() {SqlSession sqlSession = MybatisUtils.getSqlSession();StudentDao dao = sqlSession.getMapper(StudentDao.class);Student student = new Student();student.setId(1004);student.setName("亚瑟");student.setEmail("yase@qq.com");student.setAge(35);int nums = dao.insertStudent(student);sqlSession.commit();System.out.println("添加对象的数量：" + nums);}@Testpublic void testUpdateStudents() {SqlSession sqlSession = MybatisUtils.getSqlSession();StudentDao dao = sqlSession.getMapper(StudentDao.class);Student student = new Student();student.setId(1002);student.setAge(222);int nums = dao.updateStudent(student);sqlSession.commit();System.out.println("更新对象的数量：" + nums);}@Testpublic void testDeleteStudents() {SqlSession sqlSession = MybatisUtils.getSqlSession();StudentDao dao = sqlSession.getMapper(StudentDao.class);int nums = dao.deleteStudent(1003);sqlSession.commit();System.out.println("删除对象的数量：" + nums);}

在上一篇博文三、MyBatis 使用传统 Dao 开发方式的基础上，只做了以下更改：

删除dao的实现类StudentDaoImpl
修改TestMybatis的代码：

所以缺少的代码请参考三、MyBatis 使用传统 Dao 开发方式

package com.zep;import com.zep.dao.StudentDao;
import com.zep.domain.Student;
import com.zep.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;import java.util.List;public class TestMybatis {@Testpublic void testSelectStudents() {/*** 使用mybatis的动态代理机制，使用SqlSession.getMapper(dao接口)* getMapper能够获取dao接口对应的实现类对象。*/SqlSession sqlSession = MybatisUtils.getSqlSession();StudentDao dao = sqlSession.getMapper(StudentDao.class); // 这句代码可以自动创建dao接口的实现类对象//调用dao的方法，执行数据库的操作List<Student> students = dao.selectStudents();for (Student student : students) {System.out.println("学生=" + student);}}@Testpublic void testInsertStudents() {SqlSession sqlSession = MybatisUtils.getSqlSession();StudentDao dao = sqlSession.getMapper(StudentDao.class);Student student = new Student();student.setId(1004);student.setName("亚瑟");student.setEmail("yase@qq.com");student.setAge(35);int nums = dao.insertStudent(student);sqlSession.commit();System.out.println("添加对象的数量：" + nums);}@Testpublic void testUpdateStudents() {SqlSession sqlSession = MybatisUtils.getSqlSession();StudentDao dao = sqlSession.getMapper(StudentDao.class);Student student = new Student();student.setId(1002);student.setAge(222);int nums = dao.updateStudent(student);sqlSession.commit();System.out.println("更新对象的数量：" + nums);}@Testpublic void testDeleteStudents() {SqlSession sqlSession = MybatisUtils.getSqlSession();StudentDao dao = sqlSession.getMapper(StudentDao.class);int nums = dao.deleteStudent(1003);sqlSession.commit();System.out.println("删除对象的数量：" + nums);}}